LT155 Governor issue?

I've got an LT155 with a 15hp Kohler. After researching the heck out of my issue, I believe it might be the internal gear. The symptoms are that the engine will rev high but the throttle will not return. I've tried adjust the governor lever as instructed. If I move the governor lever back by hand, it returns to correct idle. I really don't want to tear the engine apart as spring has arrived. Does everyone agree that it is an internal governor issue? What would happen if I just add a return spring to the throttle to pull it back?